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BIG PHYSICS, BIG QUESTIONS –

Termite robots build castles with no human help

By Hal Hodson

A SWARM of robots scuttles across the bench. Working together, each one scoops a styrofoam block on to its back and then climbs a growing layer of blocks to flip its new one into place. Slowly, a tower rises up.

It’s impressive – especially as they are doing this without any human control at all. All they have to go on are simple rules about the environment around them.

What’s more, the bodies of these shoe-sized robots have been 3D printed, making them cheap and easy to reproduce. Their hooked wheels, good for climbing and grasping, also let them trundle on the flat.

“You can get really far with simple robots,”says Kirstin Petersen, who designed and built them as part of Harvard University’s termite-inspired TERMES project.

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“If you want to build underwater, if you want to build a Mars base, it’s going to be very difficult, dangerous and expensive to send people,” says Justin Werfel of the Wyss Institute for Biologically Inspired Engineering at Harvard University. “But if you could send a team of robots to go build the habitat as the first step – that’s the really long-term vision.”

To spur the swarm into action, Werfel gives the robots a mathematical model of the structure to be built, say, a tower or a pyramid. Each robot uses the model to calculate where it will place the next block it picks up, moving on to another spot if its planned drop-off has already been completed by another bot. It uses ultrasound and infrared sensors, as well as an internal accelerometer, to figure out how many blocks it has climbed, and where it is in relation to the structure it is building (Science, doi.org/rhm).

The project shows that controlling robots using simple, distributed rules does work. “You have a simple, cheap, expendable robot, and then you throw a bunch of them at a system and you don’t care if they break,” says Petersen.

Neri Oxman of the Media Lab at the Massachusetts Institute of Technology, who works on robotic architecture, says the concept is very promising. “This work promotes a truly decentralised construction system offering robust and customised designs,” she says. “It paves the way for emergent design based on environmental sensing and represents an important step towards enabling the shift from swarm-based construction to swarm-based design.”

Petersen and Werfel are not the only roboticists working on swarm technology. The Laboratory of Intelligent systems at the Swiss Federal Institute of Technology in Lausanne has developed a swarm of small aircraft that communicate, position themselves and find targets using nothing but sound. They have no central control system; instead their developers gave each one the ability to make decisions based on its local conditions.

And at Heriot-Watt University in Edinburgh, UK, roboticists are working on a swarm of underwater robots which they hope will one day be able to repair damaged coral reefs.

In the shorter term, Werfel says swarm bots could be used for tasks like building levees out of sandbags. “The scenarios where you want to use robots rather than humans are described by the three Ds – dirty, dangerous and dull,” he says. The group has already used a modified version of the TERMES robots to drag and stack bags of rice to make a wall.

In the shorter term, swarm bots could be used for tasks like building levees out of sandbags